Zone demand elevator system

ABSTRACT

AN ELEVATOR SYSTEM IN WHICH AVAILABLE CARS ARE ASSIGNED TO PROCEED TO ZONES OF FLOORS SELECTED IN ACCORDANCE WITH AN EFFECTIVE PATTERN OF ZONES REQUIRING SERVICE AND THE PATTERN OF CARS ALREADY SERVING CORRIDOR CALLS IS IMPROVED BY ALTERING THE EFFECTIVE PATTERN OF ZONES REQUIRING SERVICE WHEN ALL OF THE ZONES HAVING UNANSWERED CORRIDOR CALLS THEREIN HAVE BEEN PROVIDED FOR AN AN ADDITIONAL CAR BECOMES AVAILABLE SO THAT THE ADDITIONAL AVAILABLE CAR CAN BE ASSIGNED TO ASSIST IN SERVING CORRIDOR CALLS.

United States Patent lnventor Henry C. Savlno lhcliensack, NJ. Appl. No. 877,645 Filed Nov. 18, 1969 Patented June 28, 1971 Assignee Westinghouse Electric Corporation Pittsburgh, Pa.

ZONE DEMAND ELEVATOR SYSTEM 3,504,771 4/1970 Suozzoetal 187/29 Primary Examiner-Gris L. Rader Assistant Examiner-W. E. Duncanson,.1r.

At!orneys-A. T. Stratton, C. L. Freedman and R. V.

Westerhoff ABSTRACT: An elevator system in which available cars are assigned to proceed to zones of floors selected in accordance with an effective pattern of zones requiring service and the pattern of cars already serving corridor calls is improved by a1- tering the effective pattern of zones requiring service when all of the zones having unanswered corridor calls therein have been provided for and an additional car becomes available so that the additional available car can be assigned to assist in serving corridor calls.

CRCUIT (I F1G.8

PR1: M1 3,256,958

CRCUlTS OF rr or no. syn no. agsgssa CAR AND ZOE SELECTION PAT NO 3,256,958

m CRCUlTS OF PET in 3,256,956

PATENTED JUN28 |97| CSHB CX9 CIRCUIT OF FIG.8

PAT. NO. 3,256,958

CIRCUIT QF FIG. 9 PAT NO. 3,256,958

R25 R26 R27 CAR AND ZONE SELECTION CIRCUITS OF PAT NO. 3,256,958

1 D BMI6 REMAINING CIRCUITS OF PAT NO. 3,256,958

FIG.I

I INVENTOR Henry C. Sovino QWHIWIL E ATTORN i ZONE DEMAND ELEVATOR SYSTEM BACKGROUND OF THE INVENTION 1. Field of the Invention This invention relates to elevator systems and more particularly to elevator systems in which a plurality of elevator cars are arranged to serve as a bank in a structure having a plurality of landings which are divided into zones.

2. Description of the Prior Art In an effort to provide more efficient elevator service, schemes have been devised whereby the floors in a building are divided into zones and elevator cars are assigned to travel to specific zones to serve registered floor calls. Such a system is described in U.S. Pat. No. 3,256,958 which dispatches a car not committed to provide a specific form of service to proceed to the highest zone in which a down corridor call is registered. When an additional car becomes available for assignment it is assigned to approximately the midpoint of the remaining zones requiring service thereby providing a more equitable distribution of service to the remaining calls. As additional cars become available they are assigned to proceed to other zones not already provided for. Although this system provides a good distribution of cars serving down corridor calls, once all the zones having registered corridor calls have been provided for any additional cars which become available will stand idle even though they could be of assistance in serving the remaining registered corridor calls.

The application of John Suozzo and Henry C. Savino Ser. No. 675,879, filed Oct. 17, 1967 now U.S. Pat. No. 3,504,771 and assigned to the same assignee as this application discloses an elevator system wherein an additional available car is dispatched to the highest down call registered when a car has been assigned to each down zone requiring down service. In addition, the application of the same inventors Ser. No. 675, 907 also filed on Oct. 17, 1967 now U.S. Pat. No. 3,504,770 and assigned to the same assignee, discloses an elevator system wherein an additional elevator car may be assigned to a zone when a predetermined quota of calls per car already assigned to the zone have been exceeded. Although these systems provide for assigning additional available cars to zones already assigned a car, they do not take into account the overall pattern of zones requiring service and the relative position of the cars serving the zones.

SUMMARY OF THE INVENTION According to this invention the effective pattern of zones requiring elevator service is altered as the cars are assigned to those zones. When all of the zones have been so provided for, and an additional car becomes available, the effective pattern of zone demands is restored to the pattern of zones having unanswered corridor calls. According to the invention, the effective pattern of zones requiring service can be altered by blocking the zone demand signal in zones occupied by a car conditioned to serve the registered calls in the associated zone. An additional feature of the invention is that through the reestablishment of the demand pattern once all the calls have been provided for, the assignment of cars to serve calls in the zone behind a car serving calls in that zone is expedited.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a schematic circuit diagram of an elevator system embodying the invention with those portions directly effected by the invention being shown in straight line form and with the remaining portions of the circuit shown in block diagram form; and

FIGS. 2 through 4 are schematic views of an elevator installation illustrating the application of the subject invention thereto.

DESCRIPTION OF THE PREFERRED EMBODIMENT The subject invention is an improvement in the elevator system disclosed in U.S. Pat. No. 3,256,958, hence it will be described in detail as applied to the circuits illustrated in that patent hereinafter referred to as "the patent." For the purpose of disclosing a working embodiment of the invention, the patent is hereby incorporated by reference into this application. For those portions of the circuits not specifically described herein, it can be assumed that they function as illustrated and described in the patent except of course that the overall operation of the system will be modified by the subject invention.

As in the patent, the invention may be incorporated in an elevator system having any desired number of elevator cars, arranged either for attendant operation or for automatic operation to serve any desired number of floors, however, the invention may be described adequately with reference to an elevator system having three elevator cars arranged for fully automatic operation. Although the patent was applied to a building having six floors, this invention will be described as being applied to a building having seven floors in order to more clearly illustrate the operation of the invention. As in the case of the patent the floors will be divided into three zones for the purpose of serving down corridor calls. Accordingly, landings 2 and 3 are considered zone 1 which is identified by the reference character Z1, landings four and five comprise zone 2 identified as Z2 while landings six and seven constitute the third zone identified as Z3. This grouping of the landings into zones is arbitrary and the zones can encompass any number of landings as long as at least one zone includes more than one landing. As is the case of the patent the first landing or lower terminal is identified as zone Z0 since it is considered a zone for certain purposes.

Electromagnetic switches and relays employed in the control circuits may have numerous contacts of either the make or the break type. Each set of contacts of a relay or switch is designated by the reference character employed for the relay or switch, followed by a suitable numeral specific to the set of contacts. For example, the reference characters ZD2 and ZD8 designate, respectively, the second and eighth sets of contacts associated with thezone demand switch ZD. The symbols designating the contacts on the schematic view indicate whether a particular set of contacts are make or break. For instance, the contacts ZD2 are make contacts which are normally open and do not close until the relay ZD is energized while the contacts ZD8 are break contacts which are normally closed.

The three cars utilized in the system are referred to as the A, B and C car. Although some of the relays and switches utilized are common to all the cars, others are individual to each car. For instance, there is a down call assigned relay FA for each car. In keeping with the labeling system of the patent, the down call assigned relay associated with the elevator car A is identified by the reference character FA, however, the reference characters for the down call assigned relays associated with the B and C cars are preceded by the respective car identifier, i.e. BFA and CFA respectively. Therefore, throughout the patent and this application, relays and switches associated with an individual car will be preceded by the appropriate car identifier except in the case of the A car.

In order to facilitate an understanding of the invention, the apparatus illustrated in FIG. I which is specific to the car A and certain apparatus common to all the elevator cars, is set forth as follows:

Apparatus For Elevator Car A FA-down call assigned relay FR-available car relay FUup call assigned relay DB-down zone call below relay LW-load switch Mrunning relay SHdown zone assigned relay X'down preference relay Z0, Z1, Z2, Z3zone position relays.

Apparatus Common To All Cars AD-auxiliary demand relay DUup zone demand relay K0, K1, K2, K3--down zone demand registering relays KlN, K2N, K3N, cancelling coils for down zone demand registering relays ZD-down zone demand relay 2DR through 7DRdown floor call registering relays.

The invention will be described as being applied to the distribution of service to down corridor calls. It could also be applied to up corridor calls although providing equitable service to up calls is not as difficult as for down calls since most up calls in a building originate from the lower terminal floor while the down corridor calls appear randomly throughout the building.

When a prospective passenger presses the down corridor call button (not shown) at a landing, the down floor call registering relay for that floor is energized and remains energized until the elevator car answers the call. Contacts of the appropriate down call registering relay in FIG. 1 close to energize the associated down zone demand registering relay K1, K2 or K3. The down zone demand registering relay K1 is associated with the first down zone comprising the second and third floors, the relay K2 is associated with the second down zone comprising the fourth and fifth floors, while the relay K3 is associated with the third down zone which consists of the sixth and seventh floors. Each of these relays is energized by makecontacts of the down floor call registering relays for the floors in the zone with which the respective relay is associated. Each of the down zone demand registering relays K1, K2 and K3 has a canceling coil associated therewith identified by the same reference character followed by the suffix N. For example, the down zone demand registering relay K3 for the third down zone has a cancelling coil K3N wound on the same core and energized in opposition to the energization of the relay energizing coil. Consequently, when the cancelling coil is reset and drops out.

It can be seen from FIG. 1 that the down zone demand registering relay for a particular zone will be deenergized if all of the calls in the zone have been satisfied since under these conditions the contacts for all of the down floor call registering relays associated with the floors in the particular zone will be open. ln addition, the down zone demand registering relay can be dropped out even though down calls are still registered in the zone through the energization of the associated cancelling coil.

Let it be assumed that a down floor call is registered for the fourth or fifth floor (make contacts 4DR4 or 5DR4 are closed). As a result, the down zone demand registering relay K2 is energized and picked up to indicate the registration ofa demand for down service for the second down zone. Any elevator car which stops in the second down zone to answer the down floor call which is registered therein will cancel the second down zone demand for service. For example, if the elevator car A is conditioned for down travel (make contacts X9 are closed), is not fully loaded (break contacts LW3 of the load switch are closed), is located at the fourth or fifth floor (make contacts 22-3 of the second zone position relay are closed) and is not assigned to serve a particular down zone (break contacts Sl-l8 of the down zone assigned relay are closed), or if it is assigned to particularly serve the second down zone (break contacts 8H8 are opened), when it reaches such zone (make contacts 8T4 of the assigned zone stopping relay closed), and all of the zones requiring down service have not yet been provided for (break contacts AD3 of the auxiliary demand relay are closed), the following energizing circuit is established:

L1, 4DR4 or 5DR4, K2N, AD3, 22-3, 8H8 or 8T4, X9, LW3, L2. Energization of the cancelling coil KZN results in the resetting and dropout of the down zone demand registering relay K2 to indicate cancellation of the demand for down service for the second down zone. When all of the down zones requiring down elevator service have been provided for, the contacts AD3 will open to prevent energization of the associated cancelling coil so that down zone demands will be reregistered for all down zones having unanswered down corridor calls despite the presence of a car conditioned to answer down corridor calls in that zone. This is done so that additional available cars may be assigned to help answer the outstanding down corridor calls.

The down zone demand registering relay cancelling coils KIN AND K3N operate in a manner similar to that described for the cancelling coil K2N, as will be apparent by inspection of F 1G. 1.

From the preceding description, it will be understood that reference hereinto the registration of down zone demands for service refer to the conditions of the down zone demand registering relays K1, K2 AND K3. In other words, pickup of one of these relays indicates the registration of a down zone demand for service as opposed to the registration of a down floor call for service, while dropout thereof signifies the absence or cancellation of such a down zone demand. It will be appreciated that in order for one of the relays K1, K2 or K3 to be picked up, a down floor call must be registered for a floor in the associated down zone, but when such a down floor call is registered, the associated down zone demand registering relay may be dropped out as a result of the operation of its associated cancelling coil; i.e., a down floor call must be registered in order to register a down zone demand for service, but the absence of the registration ofa down zone demand for service does not necessarily indicate the absence of a registered down floor call for a floor in the associated down zone, in addition, the energization of the down zone demand registering relay does not necessarily indicate the absence of a car in the zone conditioned to answer the registered down floor calls in the zone.

Pick up of the relay K0 indicates the existence of a demand for elevator service for the first floor. This relay is energized by means other than by the registration of a down corridor call and reference should be made to FIG. 8 of the patent for an illustration of the circuits for energizing this relay.

The patent describes in great detail a scheme for assigning elevator cars to zones having their zone demand registering relays energized to provide service for the down floor calls registered in such zones. According to the scheme of the patent, a zone demand relay ZD is energized when the number of down zones requiring service exceeds the number of cars serving down calls. Energization of this relay is controlled by a bridge circuit having one arm consisting of resistors R25, R26, R27 and R28 in series, with each resistor shunted respectively by the break contacts K0-3, Kl-5, 02-5 and K3-4 of the appropriate zone demand registering relay. When none of the zone demand registering relays is energized this arm of the bridge circuit is shorted, but as the respective zone demand registering relays are picked up, the associated resistor is insorted in this arm of the bridge circuit. For instance, with the relay K2 associated with the second down zone demand registering relay energized, the contacts K2-5 are opened to insert the resistor R27 into the bridge circuit. The resistors R25 through R28 are all equal in value so that the total resistance in this arm of the bridge circuit is proportional to the number of zone demand registering relays which are energized.

The other arm of the bridge circuit is composed of resistors R31, R32, R33 and R34 in series. The resistor R32 is shunted by break contacts FAll of the down call assigned relay for the A car in series with the make contacts KB2 of the down zone call below relay associated with the A car. The resistors R33 and R34 are shunted by appropriate contacts of the down call assigned relay and down zone call below relays associated with the B and C cars respectively. The down call assigned relays, for instance FA, are energized while the associated car is being assigned to serve down calls. It will only remain energized momentarily if the car is above the down calls it is to serve, however, if the car is below the assigned down calls, the down call assigned relay will remain energized until the car reverses direction at the assigned call. The down zone call below relays, for instance KB associated with the A car, are energized at all times except when the associated car is traveling down and a down zone demand registering relay for a zone below the car is energized. It can be seen therefore, that the resistors R32, R33 and R34 will be shunted except when a car is set for down travel and there is a down zone demand registered below the car or the car is traveling up to serve a down zone demand.

The resistors R31 through R34 are all equal in value to each other and to the value of the resistors R25 through R28. it can be appreciated then, that with no down zone demands registered all of the resistors in the upper arm of the bridge circuit are shunted so that the effective resistance of this arm is zero. Under these conditions, no cars will be serving down demands so that the resistors R32, R33 and R34 are also shunted. However, the resistor R31 is always a part of the effective resistance of the lower arm of the bridge circuit. Reference to the patent will show that the relay ZD will remain deenergized unless the effective resistance in the upper arm of the bridge circuit is equal to or greater than the effective resistance in the lower arm of the bridge circuit. Therefore, it can be seen that with no zone demands registered and no cars serving down corridor calls, that the relay ZD will be deenergized. When a call is registered in for instance the second down zone, so that the second down zone demand registering relay K2 is energized to open the break contacts K2-5, the resistor R27 will be introduced into the upper arm of the bridge circuit. Since the resistor R27 equals the resistor R3], the total effective resistance in the upper arm of the bridge circuit is equal to that in the lower arm of the bridge circuit thereby resulting in the energization of the zone demand relay ZD. The relay ZD is therefore actually a master zone demand relay which is energized when there are more demands than there are cars serving those demands.

Energization of the zone demand relay ZD results in the closing of the make contacts ZD2. Reference to the patent will show that this will result in the energization of a down call assigned relay, such as FA for the A car, through appropriate car and zone selection circuits. Energization of the relay FA results in opening of the break contacts FAll thereby inserting the resistor R32 into the lower arm of the bridge circuit. Since the total effective resistance in the lower arm of the bridge circuit is now twice that in the upper arm of the bridge circuit, the relay ZD will be deenergized to indicate that a car has been assigned to serve the down zone demand in the second down zone.

As was mentioned above, if the A car is below the second down zone when it is assigned, the contacts FAll will remain open until the car reaches the second zone and reverses direction. On the other hand, it the car is above the second down zone when it is assigned thereto, the contacts K82 will remain open to insert the resistor R32 into the lower arm of the bridge circuit. if the A car is idle in the second down zone when assigned, it will complete the circuit for the cancelling coil KZN and therefore close the contacts K2-5 to deenergize the down zone demand relay ZD. It can be seen that the relay ZD serves as a master down zone demand relay which is energized whenever there is a down zone requiring down elevator service which has not been provided for. It is also clear, that the zone is provided for when there is a car on its way to serve the demand. It can be further appreciated that if a car is already in position, the down zone demand is provided for without assigning an available car. For instance, if the A car is already traveling down in the third down zone when the down zone demand registering relay K2 for the second zone is energized, the contacts K82 of the down zone call below relay KB will open to insert the resistor R32 into the lower arm of the bridge circuit thereby preventing the energization of the relay ZD.

The circuits of the patent assign the first car that becomes available to the highest zone requiring down elevator service. The next car to become available is assigned to begin serving down corridor calls at approximately the middle-zone of down zones having their down zone demand registering relay picked up. Cars which subsequently become available are assigned either to the highest down zone requiring service if there is no car assigned to such zone or above such zone, or to the midpoint of the unsatisfied demands.

According to the system disclosed in the patent, when all zones have thereby been provided for, cars which subsequently become available will not be assigned since the relay ZD will not be energized. It is desirable, however,, when calls remain unanswered, that available cars be assigned to assist down traveling cars as long as they are not needed elsewhere. The need for this would be more evident in an installation wherein there were more floors per zone, however, the principle can be readily appreciated from the simplified system illustrated.

According to the invention, when a car becomes available so that the appropriate contacts of its available car relay, such as FR20 for the A car, are closed and all the down demands as well as the up demands have been provided for so that the contacts ZD8 and DU6 are closed, then the auxiliary demand relay AD will be energized. As will be remembered from the above discussion, energization of the relay AD results in opening of break contacts of this relay in the circuits for the canceiling coils of all of the down zone demand registering relays so that the down zone demand registering relays for all down zones having unanswered down landing calls therein will be energized despite the presence of a down traveling car in the zone. Energization of these down zone demand registering relays will, in most instances, result in the energization of the relay ZD thereby initiating the assignment of the additional available car to assist in answering down corridor calls. When the relay AD is energized, holding contacts AD! shunt the ZD8 contacts to maintain a circuit for the energization of the relay AD until the car can be assigned. When the car becomes assigned, the contacts of its available car relay will open to deenergize the relay AD and the circuit will be reset. However, if more than one car is available when all of the zones have been provided for, means must be provided for resetting the AD relay. For instance, during off peak conditions when several available cars accumulate and there are no demands, the AD relay would be picked up and held in by the ADl contacts despite an increase in demand. Since as will be seen below, it is desirable not to alter the pattern of down zone demands until all the zones are provided for, it is desirable to reset the AD relay after every car is assigned to determine whether the conditions for energizing the circuit still prevail. Toward this end, contacts of the down call assigned relays and the up call assigned relays, such as break contact FAl3 and FUl2 for the A car, are inserted in series with the AD relay. This results in deenergization of the AD relay every time a car is assigned and this relay can only be reenergized if no up or down demands exist (contacts ZD8 and ZU6 are both closed).

Since the FA relay of a car assigned to travel up to serve down calls or the PU relay of a car assigned to travel down to serve up calls remains energized until the car reverses at the assigned call, contacts of the running relays for each car shunt the contacts of the associated assignment relays so that a circuit for the reenergization of the relay AD can be reestablished. This expedites the reassignment of another available car.

As indicated in block diagram form at the bottom of FIG. 1, other circuits necessary for completing a working elevator system can be found in the patent.

OPERATIONS ln order to facilitate an understanding of the invention, it would be helpful at this time to describe a few typical operations of the invention. The schematic diagrams of FIGS. 2, 3 and 4 illustrate the usefulness of the invention. in these diagrams the grouping of the landings into zones is shown by the brackets embracing the selected floors and appropriately labeled through Z3 on the left-hand side of each diagram. Registered down floor calls for selected floors are shown on the right side of each diagram by inverted triangles. The solid triangles indicate down floor calls at floors in a zone not occupied by a car serving down floor calls in that zone, while the open triangles indicate down floor calls in zones so occupied. The location of the cars is indicated by the blocks labeled with the appropriate car designation adjacent the floor position of the car. The solid arrows extending from the block indicate the direction of travel of the car. The absence of a solid arrow attached to a car block indicates that the car is available at the floor at which it is located. The dotted arrow indicates the travel of the car after it has been assigned.

FIG. 2 illustrates the operation of the invention to assign a car, which would otherwise stand idle, to assist in serving down corridor calls in zones which have already been provided for. In the situation illustrated in FIG. 2, it can be seen that the C car is at the third floor which is in the first zone and is serving in the up direction. It therefore has no effect on the service to the down corridor calls. It can also be seen that the B car is located at the seventh floor which is in the third zone and is serving down corridor calls. Finally, the A car is at rest at the second floor and is available for service.

Assume now that down corridor calls are registered at the fourth, fifth and sixth floors. The registration of the down calls at the fourth and fifth landings results in the closing of the contacts 4DR4 and SDR4 to provide parallel circuits for the energization of the down zone demand registering relay K2 for the second zone. Furthermore, the registration of the down corridor call at the sixth landing results in the closing of the contacts 6DR4 thereby providing a circuit for the energization of the down zone demand registering relay K3 for the third zone. However, the relay K3 will not be picked up because with the B car at the seventh floor (make contacts BZ3-3), not assigned to a lower down zone (break contacts BSH8), set for down travel (make contact BX9), not fully loaded (switch BLW3) and since at this point the relay AD is deenergized so that the contacts AD2 are closed, the cancelling coil k3N for the down zone demand registering relay associated with the third down zone will be energized.

Under these circumstances the down zone demand relay ZD will not be energized since with only the down zone demand registering relay for the second down zone energized, only the resistor R27 will be introduced into the upper arm of the bridge circuit by the opening of the break contact K2-5. On the other hand, the resistors R31 and R33 (since the contacts BKBZ will be open with a demand registered in a zone below the B car), will be inserted in the lower arm of the bridge circuit. Thus, the total effective resistance in the lower arm of the bridge circuit will exceed that in the upper arm of the bridge circuit and the relay ZD will remain deenergized. Therefore, without a master down demand registered, the A car will remain idle.

However, with the A car available, its contacts F020 will be closed. Since there is no down demands unprovided for (contacts ZD8 closed) and it will be assumed at this point that there are no up demands registered (contacts DU6 closed) and since the cars at this time are not in the process of being assigned so that the up and down call assigned relays for all of the cars are deenergized, the auxiliary demand relay AD will be energized. Energization of the AD relay results in opening of the break contacts AD2 through AD4 in the cancelling circuits for each of the down zone demand registering relays. The opening of the contacts AD2 results in the dropout of the cancelling coil K3N. Since a down call is still registered at the sixth floor, the relay K3 remains energized at this time. Pickup of the relay K3 results in the opening of the K34 break contacts in the upper arm of the bridge circuit to introduce the resistor R28 into this circuit. With the resistors R27 and R28 in the upper arm of the bridge balancing the resistors R31 and R33 in the lower arms of the bridge, reference to the patents will show that the relay ZD will be energized. Pickup of the relays ZD results in the closing of the contacts ZD2 to initiate the assignment of the A car to serve down corridor calls through the energization of the relay FA.

According to the assignment circuits of the patent, with down call demands registered in the second and third down zone and with a car above all the down calls, the available car is assigned to the second down zone. Therefore, as indicated by the dotted arrow in FIG. 2 the A car will proceed to the highest down call in the second zone, which is at the fifth floor, and reverse. As a result, the B car will serve the down call at the sixth floor and the A car will serve the down calls at the fifth and fourth landings. It can be seen that although the down calls in the second and third zone were provided for,

more efficient use of the cars in the system was achieved I through the operation of the subject invention.

FIG. 3 illustrates how the invention is also useful in expediting the assignment of an available car. In the situation illustrated therein, the B car is stopped at a down floor call registered at the fourth floor which is in the second down zone. The C car is at the lower terminal floor and has been selected as the next car to be dispatched in the up direction therefrom. Reference to the patent will show that this next car designation is an indication that the C car is being held at the lower terminal floor in order to receive passengers desiring travel in the upward direction. The A car in the situation illustrated in FIG. 3 is available at the second floor.

It can also be seen from FIG. 3 that a down corridor call is registered at the fifth floor. Registration of this down call results in closing of the contacts 5DR4 to complete a circuit for the energization of the down zone demand registering relay K2 for the second down zone. However, it will also be clear from the discussion of the situation considered in FIG. 2, that the cancelling coil of K2N for the second down zone demand registering relay would be energized if the subject invention was not in use.

A glance at FIG. 3 will indicate that a car is going to have to be assigned to the down call at the fifth floor, however, as long as the B car remains at the fourth floor serving the down call registered thereat, no master down demand can be created in order to assign a car to the fifth floor. When the B car has answered the call at the fourth floor and leaves the second down zone, a demand will be registered at the second down zone and the A car will be assigned thereto. However, since the A car is available and there are no up or down zone demands registered, the relay AD will be energized to open the contacts AD3 thereby deenergizing the cancelling coil KZN. This will result in the opening of the break contacts K2-5 to introduce the resistor R27 into the upper arm of the bridge circuit. Since there are no down zone demand registering relays energized for a floor below the B car the contacts BKD2 associated with the B car will be closed. Since the down call assigned relay for the B car is also deenergized, the contacts BAFll will also be closed so that the resistor R33 in the lower arm of the bridge circuit will be shunted. Since the resistors R32 and R34 associated with the A and C cars respectively are also shunted under the assumed circumstances, the only resistor in the lower arm of the bridge circuit is R31. With the bridge circuit balanced the relay ZD will be energized. The A car will be assigned and therefore begin its upward travel to the fifth floor before the 8 car has left the second down zone.

FIG. 4 illustrates the point that in order to achieve better distribution of the cars in service, the down zone demands in a zone occupied by a car serving down calls should be cancelled until all of the zones requiring service have been provided for. In the situation represented by FIG. 4, the C car is traveling in the up direction at the second floor serving up corridor calls, the B car is located at the seventh floor serving down corridor calls and the A car is available at the fifth floor. In addition down calls are registered at the sixth, fourth, third and second floors. With this distribution of down calls the circuits will be completed for the energization of the down zone demand registering relays K1, K2 AND K3, however, the presence of the B car in the third down zone traveling in the down direction will result in energization of the cancelling coil K3N to prevent the pickup of this relay. Therefore, with the resistors R26 and R27 in the upper arm of the bridge circuit and only the resistors R31 and R33 in the lower arm of the circuit, the bridge is balanced and the relay ZD will be energized indicating that there are more down zones requiring down service service than there are cars serving in the down direction.

With down demands thus registered for the first and second down zones, the zone selection circuits of the patent will assign the A car to proceed to the highest down call in the first zone and begin serving down calls from that point. It can be seen then from FIG. 4 that the A car will serve the down calls at the third and second floors while the D car will serve the down calls at the sixth and fourth floors. It will be clear from reference to FIG. I that even though the contacts FR of the available car relay for the A car are closed, the relay AD cannot be energized since the contacts ZD8 of the down zone demand relay are open.

Assume for a moment however, that the B car traveling down in its third zone was prevented from cancelling the down demand in that zone. With down demands registered in the first, second and third down zones the selection and assignment circuits of the patent would assign the A car to the second down zone. In that event, the A car would open its doors and serve the down call to the fifth floor while the B car was serving a down call to the sixth floor. Thereafter the A and B cars would leap-frog down serving the down calls below. Thisbunching of the cars would result in inefficient and inequitable service to the down calls below.

It is seen therefore that it is desirable to cancel the demands in zones provided for when all of the zones are not taken care of in order to provide for more efficient utilization of the available cars. However, after a car is in position to serve each of the down zones requiring down service it is desirable to reestablish demands in all zones having down calls registered if there is an available car standing idle so that it may be assigned to help out.

The illustration given should not be considered as a limitation on the scope of the invention. It will be understood by one skilled in the art that numerous modifications and applications could be made within the scope and spirit of the invention.

I claim:

1. In an elevator system a structure having a plurality of landings, said landings being divided into zones with at least one zone having at least two landings therein, a plurality of cars mounted for movement relative to the structure to serve the landings, and control means for controlling the movement of the car between the landings, said control means including call registering means operable for registering a call for service from a plurality of said landings, availability means associated with each of a plurality of said cars and operable to condition the associated car to be available for assignment to serve registered calls, assignment means for assigning an available car to proceed to a zone having a registered call when no car is in position to serve the call until all such zones are provided for, said assigning means including means for selecting the zone to which the cars are to be assigned from a plurality of zones requiring service according to the pattern of such zones and the pattern of cars already serving those calls, and additional means operative to assign an additional available car to a zone already provided for only after all other zones having registered calls have been provided for.

2. The system of claim 1 wherein said call registering means comprises means operative to register calls for service in a first direction from each of a plurality of said landings and including means for indicating when all zones having registered first direction landing calls are provided for including means responsive to the presence of at least one car conditioned to serve first 'direction landing calls displaced in the second direction from each zone having a registered first direction landing call and not occupied by a car conditioned to serve first direction landing calls within the zone for each such zone.

3. The system of claim 1 wherein the additional means includes means operative in the presence of an available car after all the zones have been provided for to reestablish a need for a car in a zone already provided for yet having registered calls still unanswered therein whereby said assignment means can assign the available car to assist in serving registered calls.

4. In an elevator system a structure having a plurality of landings, said landings being divided into zones with at least one zone having at least two landings therein, a plurality of cars mounted for movement relative to the structure to serve the landing, and control means for controlling the movement of the cars between the landings, said control means including call registering means operable for registering a call for service from a plurality of said landings, availability means associated with each of a plurality of said cars and operable to condition the associated car to be available for assignment to serve registered calls, zone demand means responsive to the registration of a call in a zone for registering a demand for service for the associated zone, modifying means operative under first predetermined conditions to render selected zone demand means ineffective thereby generating a pattern of effective zone demands, assignment means responsive to the effective pattern of zone demands and the pattern of cars serving registered calls for determining the assignment of available cars to serve the registered calls and disabling means operative under second predetermined conditions to disable the modifying means.

5. The system of claim 4 wherein said call registering means comprises means for registering a call for service in a first direction from each of a plurality of said landings, wherein said zone demand means are operative to register a demand for service in said first direction when a first direction call is registered in the associated zone, wherein said assignment means is operative to assign available cars to serve the first direction calls, and wherein the modifying means includes means responsive to the presence of a car in a zone conditioned to serve first direction calls within the zone for rendering the associated zone demand means ineffective despite the presence ofa registered first direction call within the zone.

6. The system of claim 4 wherein said disabling means includes means operative to disable said modifying means in response to the presence of a car in position to serve each of the effective zone demands.

7. The system of claim 6 wherein said disabling means includes means operative to disable the modifying means only in response to the presence of an additional available car.

8. The system of claim 5 wherein said disabling means includes means operative to disable said modifying means in response to the presence of a car in position to serve each of the effective first direction zone demands including cars assigned by the assigning means to travel in the second direction to reach the assigned first direction calls, said disabling means being operative to disable the modifying means only when an available car is present.

9. In an elevator system a structure having a plurality of landings, said landings being divided into zones with at least one zone having at least two landings therein, a plurality of cars mounted for movement relative to the structure to serve the landings, and control means for controlling the movement of the cars between the landings, said control means including call registering means operable for registering a call for service from a plurality of said landings, availability means associated with each of a plurality of said cars and operable to condition the associated car to be available for assignment to serve registered calls, zone demand means associated with a plurality of zones and operable in response to the registration of a call at a landing within the zone to establish a demand for service to the associated zone, master zone demand means operable from a first condition to a second condition in response to the presence of zone demands in excess of the number of cars serving registered calls, assignment means responsive to the operation of the master zone demand means to the second condition for assigning an available car to serve the registered calls, cancelling means operable to cancel a zone demand when a car serving registered calls enters the asserving registered calls in the zone whereby additional available cars are assigned to serve registered calls whenever they can be of assistance.

r I I UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. 3,587 786 Dated June 28, 1971 Henry C. Savino Inventor(s It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

Column 8, line 49, "BKD2" should read BKB2 Column 8, line 51, "BAFll" should read --BFA ll Column 9, line 6, cancel "service".

Column 9, line 12, "D" should read B Column 9, line 47, "car" should read car's Signed and sealed this 25th day of January 1972.

(EEAL) fittest:

TWIJARD M. FLETCHER, R

testing Officer ROBERT GOTTSCHALK Commissioner of Patents FORM PO-105O {10-69) U5COMM-DC GOB'IS-PBQ Q U 5 GOVERNMENT PRINTING OFFICE 1969 O35E-334 

